Rheostat.



' T. s. PERKINS. l; 5 3? RHBOSTAT. XXS ArrLIonIoN FILED Nov.1a. 1902.

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RHEOSTAT.

APPLIUATION FILED Nov.13. 1902.

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' To all whom it may concern..-

Be it known that I, THOMAS S. PERKINS, a citizen ofthe United States, residing in Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful' Improvement in Rheostats, of

which the Afollowing Vis a specification.

My invention relates to apparatus em ployed in connection with the operation of electrical Y thereby or supplied thereto; and ithas forits object to provide a rheostat element or -resistance-box of simple and inexpensive construction and one which may be readily assembled, thoroughly ventilated, and be enicient and durable in use.`

In the operation of electric motors, notably the large and frequent variations in speed and the prevention of rushes of current in starting ordinarily necessitate the employmentof considerable ohmic resistance, which is cut into and out of circuit in accordance withthe exgencies of the service.

In order that the amount of resistance may be varied over a considerable range, several elements are usually employed, which are preferably of like construction land are cut into and out of circuit by means of a suitable controlling-switch. My present invention is well adapted to this service, but may also be utilized in vany relation where ohmic resistance is needed.

. Myinvention is illustrated in the accompanying drawings, in Which- Figure 1 is a side elevation of a resistance broken away. Fig. 2 is a plan view, and Fig. 3 is an end elevation, of the apparatus shown iiFig. 1.

The resistance portion ofthe box or structure l consists of a set of grids 2 of zigzag formation and for convenience and cheapness of construction will generally be of iron and cast in suitable molds. These grids may be otherwise formed and may be made of other material than iron, if desired; but on account of cheapness of materialan'd facility of manufacture cast-iron is preferred.

5o Each end of each grid terminates in a limb if' UNITED vSPECIFIC'A'JTION formingpart of Letters Patent N o. 740,175, dated September 2,9', I

Application led November 13, 1902.. Serial No. l31|134 (No model.) I V E to machines for varying'the currents generated- ,those employed for driving railway-vehicles;

box or structure, a portion of the same being u. aocupu mupuelnuel Z3, LSUSJ.

NT OFFICE. i

THOMAS s. PERKINS, or WILII'INsRURe.,` PENNSYLVANIA, AssIcNoR 'roff WEsTINGHoUsE ELEcTRIc a MANUFACTURING COMPANY, AcoRI oRA-;7,

3 of a little more than half the length futh'eg` intermediate portions and of considerably; greater cross-section.v-` This limb. terminates". in 'af-hollow boss 4, havinga lug or projection' t5, the outer face ofwliichinay bea plainsur face for the purpose of receiving a connect-' .ing plate or 'strip 6; Adjacent projections 5 -are joinedby means of the strips o'r plates 6";

and screws 7, the strips Orates'being `of such length as to connect the grids in circuit 6o. in the desired order. As indicated in the drawings, the grids are all connected in series; but-obviously the plates may be of such dimensions as to connect the grids either all in multipleorin such multiple-series arrangement as may be found desirable. Each set of grids formed by the connecting strips ,0I-v, plates 6 is separated from the adjacent setiA ,by insulating-Washers 8. The sets of grids thus arranged and combined may be connect- 7o ed in .circuit by means of terminal posts 9, which may be screwed into any two of the projections 5 in lieu of the screws '7. If the grids are all to be connected in circuit, the` posts will .b e mounted upon the projections. 5 'of the end grids, as indicated in Figs. l and 2 of the drawings. In order to support the parts thus far described, I provide two end plates 10, here shown as of open-work construction in order 8o twgntilation and also to lighten the structure, and I connect Vthese end plates by means of two bolts 11 at the top, two similar bolts 12 at the bottom, and two bolts 13 at each side and substantially midway betweenf' 85 the top and bottom, the latter extending through the hollow bosses 4 and the washers` 8 and being surrounded by insulatingeptubesfl 14, so as to insure electrical connection of the grids in the desired relation in the circuit; l9o The connecting strips or plates 6 are preferably formed of copper or other good conducting material, so as to insure good electrical connection between adjacent grids, notwithstanding rough treatment, exposure to the weather, or expansion and contraction by reason of heating and cooling, which may tend to produce, imperfect Contact between the meeting'sides of the bosses. Y E

The structure shown and described andtoo constituting my invention may be'supported by means of plates or bars 15, which are boltventilated, tends to eliminate objectionable vibration and strains, and issimple and inexpensive in construction'.

The form and dimensions of the structure as a whole and of the constituent parts may of course be varied from what is shown without departing from my invention.

I claim as my invention- 1. An electrical resistance structure comprising a frame, a set of grids of zigzag formation clamped therein and provided with end bosses having plane surfaces perpendicular to the planes of the grids, and strips or plates of relatively good conductivity fastened to the said plane surfaces of adjacent bosses. j 2. An electrical resistance structure comprising a frame, a set of cast-iron grids of zigzag formation severally provided with bosses at their ends having plane surfaces perpendicular to the planes of the grids, strips or plates of relatively high conductivity fastened to the said plane surfaces of adjacent bosses so as to connect the grids in the desired relation and insulating-washers .between the sets of bosses so connected.

3. An electrical resistance structure comprising a frame, a set of castmetal lgrids of zigzag formation severally provided with end bosses having plane surfaces perpendicular to the planes of the grids, insulating-washers so disposed between the bosses as to connect the grids in series and plates or strips of relatively good conductivity closely fitted and fastened to the said plane surfaces of the several sets of bosses that are included between adjacent washers.

4. An electrical resistance structure comprisinga set of cast-metal grids of zigzag formation provided with hollow bosses at their ends having plane surfaces perpendicular to hgglenes of the grids, plates of relatively good conductivity so fastened to said plane surfaces as to connect the grids in circuit in- 5 the desired manner, insulating-washers' for separating the sets of bosses and a frame consisting of end plates and connecting-bolts two of which extend through the sets'of bossesand insulating-washers. 5

5. An electrical resistance structure com? prising a set of grids of zigzag formation each' of Ywhich has end limbs of relatively large cross-section and terminating in bosses having plane surfaces perpendicular' to the 6 planes of the'grids, and connect ipggslips 'fastened to said plane surfaces.

6. An electrical resistance structure coml prising a plurality of grids of zigzag formation each of which has short end limbs of .6

relativelylarge cross-section and terminating in perforated bosses having plane surfaces perpendicular to the planes of the grids,. metal strips fastened to said plane surfaces to connect said bosses in the desired relation, 7

perpendicular tothe planes of the grids, 8

metal strips fastened to said plane surfaces to connect said bosses in the desiredelec tricalrelation and a frame comprising end plates and bolts or rods two of which extend through the grid-bosses' and are insulated 8 therefrom.

In testimony whereof I have hereunto subscribed my name this 31st day of October, 1902.

THOMAS S. PERKINS. vVitnesses:

JAMES B. Yonne, BIRNEY I-IINEs. 

